1. Field of the Invention
The present invention relates to an antenna feeding system installed at a station such as an earth station for tracking and controlling an artificial satellite hereinafter referred to as a satellite, particularly relates to an antenna feeding system for shared application of a circularly polarized wave and a linearly polarized wave.
2. Description of the Prior Art
FIG. 9 is a block diagram for a conventional antenna feeding system. 1 is a 180xc2x0 polarizer for rotating the plane of polarization of a linearly polarized wane signal transmitted from a satellite, 2 is a 90xc2x0 polarizer for passing through the signal transmitted from the satellite leaving as it is when the wave is linearly polarized and for resolving the signal into perpendicularly intersecting two linearly polarized waves when the wave is circularly polarized, 3 is a rotary joint for rotating the 180xc2x0 polarizer 1 and the 90xc2x0 polarizer 2, respectively, 4 is an orthomode transducer for dividing the perpendicularly intersecting two waves to each wave, 5 is a diplexer for dividing a signal consisting of signals having different frequencies and 6a, 6b, 7a, and 7b are signal terminals for outputting signals with respective polarization and respective frequency among different polarizations and frequencies.
A description on a conventional antenna feeding system will be given. By means of the rotary joint 3, the 90xc2x0 polarizer 2 is coupled rotatably with the 180xc2x0 polarizer 1 and with the orthomode transducer 4, and the 90xc2x0 polarizer 2 is capable of setting an arbitrarily chosen angle with respect to the orthogonally intersecting polarized wave terminals of the orthomode transducers 4. Within the 90xc2x0 polarizer 2, a dielectric plate is disposed and the angle of this dielectric plate with respect to the orthomode transducer 4 becomes a setting angle of the 90xc2x0 polarizer 2. As to the orthomode transducer 4, two transducers of 4a and 4b are disposed on the output side of the 90xc2x0 polarizer 2, and these transducers 4a and 4b have orthogonally polarized wave terminals, respectively. The diplexers 5a and 5b are connected with the orthomode transducers 4a and 4b and the signals processed in the diplexers 5a and 5b are arranged to be outputted to the signal terminals 6a, 6b, 7a and 7b. To these terminals 6a, 6b, 7a and 7b, frequency and polarization of input and output signals are allocated and respective signals, whose frequency and polarization are coincident with allocated ones, are inputted or outputted.
Subsequently, an operation of the conventional antenna feeding system for receiving a signal from a satellite will be described with reference to FIG. 9. Concretely, at first operation of receiving circularly polarized wave signals having frequencies of f1 and f2 and then receiving linearly polarized wave signals having frequencies of f1 and f2 will be described.
Now, the linearly polarized wave is the one having a polarization whose direction of propagation of an electric field is directed to a constant direction, and there exists orthogonally intersecting linearly polarized waves such as a vertically polarized wave V and a horizontally polarized wave H; the electromagnetic wave having orthogonally intersecting planes of polarization such as a vertically polarized wave V and a horizontally polarized wave can be utilized for transmission of different information by treating those waves as independent waves even when the frequencies are identical, and thus the reclamation of frequencies utilizing the orthogonally polarized wave becomes feasible. The circularly polarized wave is the one which is composed of a horizontally polarized wave H and a vertically polarized wave V with mutual phase difference of 90xc2x0, and depending on lag or lead of the phase difference, the circularly polarized wave becomes either a right handed circularly polarized wave R or a left handed circularly polarized wave L. Planes of the polarization of these waves rotate with period of the carrier wave clockwisely or counter-clockwisely and those waves intersect perpendicularly capable of carrying different information as independent electromagnetic waves, respectively.
Next, a description will be given on the operation of the antenna feeding system when it receives circularly polarized waves having frequencies of f1 and f2 transmitted from a satellite. Rotate the 90xc2x0 polarizer 2 by the rotary joint 3 and set the dielectric plate within the 90xc2x0 polarizer 2 so that the plate makes an angle of 45xc2x0 with respect to the orthogonally intersecting polarized wave terminals of the orthomode transducers 4a and 4b. For receiving a circularly polarized wave, the 180xc2x0 polarizer 1 can be set to an arbitrarily chosen position. The circularly polarized wave transmitted from a satellite is inputted to the 90xc2x0 polarizer 2 through the 180xc2x0 polarizer 1. When the circularly polarized wave inputted to the 90xc2x0 polarizer 2 is right handed R, upon converting the right handed circular wave R to a vertically polarized wave V, it is outputted to the orthomode transducer 4a, and is transmitted to the diplexer 5a together with its energy.
On the other hand, when the circularly polarized wave inputted to the 90xc2x0 polarizer 2 is left handed wave L, this wave is converted to a horizontally polarized wave H and is outputted to the orthomode transducer 4b though the orthomode transducer 4a and transmitted to the diplexer 5b together with its energy.
Through procession of the 90xc2x0 polarizer 2, the incoming circularly polarized wave is identified as to whether the wave is right handed circularly polarized wave or left handed one.
The diplexer 5a and 5b perform procession of dividing the vertically polarized wave V and the horizontally polarized wave H with respect to the frequency, and divided signals through diplexers 5a and 5b are outputted to the signal terminal 6a, 6b, 7a and 7b: if the incoming signal is the right handed circularly polarized wave R with frequency of f1, the signal is outputted to the terminal 6a and if the signal is left handed circularly polarized wave L with a frequency of f2, the signal is outputted to the terminal 7a. 
Likewise if the incoming signal is right handed circularly polarized wave R with a frequency of f2, the signal is outputted to the terminal 6b and if the incoming signal is left handed L with a frequency of f2, the signal is outputted to the terminal 7b. In this way, the incoming signal can be drawn through an appropriate terminal depending on the frequency and polarization of the incoming wave.
Next, operation on reception of linearly polarized waves having frequencies of f1 and f2 will be described.
Rotate the 180xc2x0 polarizer 1 by means of the rotary joint 3 and set the dielectric plate within the 180xc2x0 polarizer 1 so that the angular position becomes one corresponding to the angular position of the plane of the receiving linearly polarized wave. Concretely, when the plane of the polarization of the incoming wave makes an angle a with respect to the vertical axis, the dielectric plate within the 180xc2x0 polarizer is positioned so that it makes angle of a, and the 90xc2x0 polarizer 2 is set so that the dielectric plate within it makes angle of 0xc2x0 or 90xc2x0 with respect to the orthogonally intersecting polarized wave terminals of the orthomode transducers 4a and 4b. For reception of a linearly polarized wave, the 90xc2x0 polarizer 2 can allow the linearly polarized wave passing through untouched by setting the 90xc2x0 polarizer 2 to 0xc2x0 or 90xc2x0.
A linearly polarized wave transmitted from a satellite is inputted to the 180xc2x0 polarizer 1 and is converted so that the polarization plane becomes either vertical or horizontal.
Thus converted linearly polarized wave through the 180xc2x0 polarizer 1 passes through the 90xc2x0 polarizer 2 as is and is inputted to the orthomode transducers 4a and 4b. When the inputted linearly polarized wave is a vertically polarized wave V, it is divided through the orthomode transducer 4a and when that wave is a horizontally polarized wave H, it is divided through the transducer 4b. The vertically polarized wave signal V and the horizontally polarized wave signal H divided through the orthomode transducers 4a and 4b, respectively are transmitted to the diplexers 5a and 5b, respectively.
Processions of those vertically polarized wave signals V and the horizontally polarized wave signals H after being inputted to the diplexers 5a and 5b are the same as that of reception of the circularly polarized wave.
FIG. 8 shows a combination of polarizations capable of simultaneous reception of signals with different frequencies. A conventional antenna feeding system is capable of, as shown by FIG. 8 (a), simultaneous reception of circularly polarized waves with frequencies of f1 and f2 or those of linearly polarized waves with frequencies of f1 and f2. The unit for switching the reception mode for simultaneous reception of circularly polarized waves with frequencies of f1 and f2 and for those of linearly polarized waves with frequencies of f1 and f2 is simply the 90xc2x0 polarizer 2; a conventional antenna feeding system performs mode switching for allowing a simultaneous reception by setting the 90xc2x0 polarizer 2 to 45xc2x0 for reception of circularly polarized waves with frequencies of f1 and f2 and by setting it to 0xc2x0 or 90xc2x0 for reception of linearly polarized waves with frequencies of f1 and f2.
The conventional antenna feeding system gives rise to a problem such that simultaneous reception of differently polarized waves is impossible. The reason is that setting angle (of the dielectric plate) of the 90xc2x0 polarizer is different depending on the polarized wave being circular or linear: conventional antenna feeding system, after the 90xc2x0 polarizer is set to either one of its polarization modes, signals having different frequencies can be divided only from simultaneously received waves having the same polarization.
However, an antenna feeding system enabling simultaneous transmission/reception of signals with different polarization is urgently needed in order to solve the problem arising from the congested frequency band due a rising demand for utilizing the electromagnetic wave in future.
The present invention is made in order to solve the problem mentioned above.
The prime object of the invention is to provide an antenna feeding system enabling a simultaneous transmission/reception of wave signals having different frequencies of f1 and f2 with different polarization such as a circular polarization and a linear polarization.
Also the object of the present invention is to provide an antenna feeding system enabling to arbitrarily switching the combination of frequency and polarization allowing transmission/reception depending on a signal being applied to a predetermined communication system.
An antenna feeding system according to the present invention comprises orthomode transducers for resolving simultaneously received circularly polarized wave signal and linearly polarized wave signal into a vertically polarized wave signal and a horizontally polarized wave signal and for outputting each of said vertically polarized wave signal and the horizontally polarized wave signal with respect to each polarization, a first diplexer for dividing the vertically polarized wave signal outputted from said orthomode transducer with respect to frequency and for outputting said vertically polarized wave signal having the same frequency with that of the circularly polarized wave signal to a signal path, which is allocated to the frequency of circularly polarized wave signal, and for outputting said vertically polarized wave signal having the same frequency with that of said linearly polarized wave signal to a signal terminal provided for the vertically polarized wave signal, a second diplexer for dividing the horizontally polarized wave signal outputted from the orthomode transducer with respect to frequency and for outputting said horizontally polarized wave signal having the same frequency with that of the circularly polarized wave signal to a signal path, which is allocated to the frequency of said circularly polarized wave signal, and for outputting the horizontally polarized wave signal having the same frequency with that of the linearly polarized wave signal to a signal terminal provided for the horizontally polarized wave signal, and a hybrid circuit for synthesizing said signals transmitted from said first diplexer and the second diplexer through the signal paths, which are allocated to frequency of said circularly polarized wave signal, upon giving phase difference of ninety degrees between the signals and for outputting the synthesized signal selectively to either of a signal terminal provided for the right-handed circularly polarized wave signal or a signal terminal provided for the left-handed circularly polarized wave signal with respect to type of said circularly polarized wave signal.
In an antenna feeding system according to the present invention, selector switches, which perform switching destinations of output signals being divided by the first diplexer and the second diplexer between the hybrid circuit and the signal terminals, are disposed between the diplexers and the hybrid circuit.
In an antenna feeding system according to the present invention, with respect to the circularly polarized wave signal inputted into said orthomode transducers, the selector switches connect the signal paths being allocated to said frequency of the circularly polarized wave signal to the hybrid circuit so that signals outputted from the first diplexer and from said second diplexer are inputted to said hybrid circuit, and with respect to said linearly polarized wave signal inputted into said orthomode transducers, the selector switches connect said signal paths being allocated to said frequency of the linearly polarized wave to predetermined signal terminals so that signals outputted from the first diplexer and from the second diplexer are inputted to the signal terminals.
In an antenna feeding system according to the present invention, said hybrid circuit synthesizes signals being inputted through phase shifters for compensating phase difference of signals which are divided with respect to frequency by said first diplexer and the second diplexer.
An antenna feeding system according to the present invention, said hybrid circuit synthesizes signals being inputted through phase shifters for compensating phase difference of signals which are divided with respect to frequency by said first diplexer and the second diplexer.
A antenna feeding system according to the present invention comprises orthomode transducers for resolving simultaneously received circularly polarized wave signal and linearly polarized wave signal into a vertically polarized wave signal and a horizontally polarized wave signal and for outputting each of the vertically polarized wave signal and the horizontally polarized wave signal with respect to each polarization, a first diplexer for dividing the vertically polarized wave signal outputted from said orthomode transducer with respect to frequency and for outputting the vertically polarized wave signal having the same frequency with that of the circularly polarized wave signal to a signal path, which is allocated for the frequency of the circularly polarized wave signal, and for outputting the vertically polarized wave signal having the same frequency with that of said frequently polarized wave signal to a signal terminal provided for the vertically polarized wave signal, a second diplexer for dividing the horizontally polarized wave signal outputted from the orthomode transducer with respect to frequency and for outputting said horizontally polarized wave signal having the same frequency with that of the circularly polarized wave signal to a signal path, which is allocated to the frequency of said circularly polarized wave signal to a signal path, and for outputting the horizontally polarized wave signal having the same frequency with that of the linearly polarized wave signal to a signal terminal provided for the horizontally polarized wave signal terminal, and a first orthomode transducers being connected to said first diplexer and to the second diplexer through the signal paths being allocated to the frequency of the circularly polarized wave signal and for synthesizing the signals, which are transmitted through the paths from the diplexers, to a circularly polarized wave signal, a first 90xc2x0 polarizer for outputting a vertically polarized wave signal when the circularly polarized signal transmitted from the first othromode transducer is right-handed, and for outputting a horizontally polarized wave signal when the circularly polarized wave signal transmitted from the first orthomode transducer in left-handed, and a second orthomode transducer for outputting a signal to a predetermined signal terminal depending on wave signal outputted form the 90xc2x0 polarizer being vertically polarized or being horizontally polarized.